An anonymous Brooklyn-based LLC has filed applications for a five-story, nine-unit mixed-use building at 181 North 7th Street, in northern Williamsburg. The project will measure 14,523 square feet. It will include a 1,972-square-foot medical office on the ground and cellar levels, followed by residential units on the second through fifth floors. The apartments should average 891 square feet, which means either rentals or condos could be in the works. Michael Avramides’s Midtown East-based architecture firm is the architect of record. The 50-foot-wide, 5,000-square-foot lot is occupied by a two-story residential building. Demolition permits were recently filed.